Differential-microphone repeater.



J. J. GOMBR.

DIFFERENTIAL MICROPHONE REPEATER.

APPLEATION FILED FEB.27,1911. 1 Q89 534 Patented Mar. 10, 1914.

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WITNESfiES J. J. OOMBRQ DIFFERENTIAL MICROPHONE REP EATER.

APPLICATION rum) rmmv. 1911.

1 ,089,534. Patented Mar. 10, 19m

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I d7 F .66 m 6 I UNITED STATES PATENT OFFICE.

JOHN J. COMER, OF CHICAGO, ILLINOIS, ASSIGNOR TO AUTOMATIC ENUNCIA'IOR COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

DIFFERENTIAL-MICROPHONE BEPEATER.

Specification of Letters Patent.

Application filed February 27, 1911. Serial No. 611,111.

To all whom, it may concern.

Be it known that I, JOHN J. COMER, a citizen of the United States of America, and resident of Chicago, Cook county, Illinois, have invented a certain new and useful Improvement in Difierential-Microphone Repeaters, of which the following is a specification.

My invention relates to microphone transmitters in general, but more particularly to microphones of the socalled differential .peater, pass through both walls thereof, but

only through one, whereby the construction and mode of operation are simplified, and whereby the method of regulating the air gap provided between a flexible diaphragm and a magnet, which diaphragm serves as the armature and is the said springy or resilient member connected with said stem, is rendered more satisfactory than heretd fore, as will hereinafter more fully appear.

To the foregoing and other useful ends, my invention consists in matters hereinafter set forth and claimed.

In the accompanying drawings Figure 1 is a view on one side of a differential microphone repeater with the casing thereof removed to show the construction. Fig. 2 is a 'imilar view of another side of said repeater. Fig. 3 is a view similar to Fig. 2, showing some of the parts separated. Fig. at. is an enlarged longitudinal section of the forward end portion of the repeater shown in preceding figures, the rear end thereof being shown broken away for convenience of illustration. Fig. 5 is a front elevation of the said repeater, on the same scale as Figs. 1, 2 and 3. Fig. 6 is an end view, on the same scale as Fig. 5, of the magnet structure with the cap or microphone removed. Fig. 7 is a View of the inside of the said cap as it appears when removed from the structure of the repeater.

As thus illustrated, the permanent magnet A has the pole pieces a, which are arranged to engage the opposing surfaces of the limbs a, being separated and held in place by the block a? that encircles the bolt at. The said limbs are provided with brackets a secured thereto, and the said bolt extends through the said bracket and the limbs of the magnet, and through the said pole pieces and the said block, whereby the magnetstructure is clamped tightly together. A block of insulation (4 is secured to the top of said bolt by a small screw (1., and this lock of insulation carries the two binding posts a and a whereby suitable circuit con-- nections can be made. The pole pieces a have windings a, and these electromagnets are partially inclosed by a cup at, the back of which is secured to the bracket a the back of said cup being apertured to receive the said polarized electromagnets. A cup 0. closes the open front of the said cup, being screwed thereon, thus forming a front wall for the box or chamber in which the electromagnets are partially inclosed. A ring of insulation bears against the wall of said cap, and a metal ring a is superimposed thereon, whereby a shoulder is formed for the marginal portions of the diaphragm a, which latter is of any suitable material, preferably metal of a parai'nagnetic character. The said diaphragm is held in place by a ring of insulation (4, which bears against the other side thereof, and near the margin, and by a metal ring a that screws into the threaded interior of the cap, which ring is provided with notches a by which it can be screwed into place to clamp the dia phragm tightly in position. The metal ring a may be used as a terminal ring for malting electrical connection, So far, it will b;- seen that the structure resembles an ordinary receiver, as the diaphragm a will be vibrated by the telephone currents passing through the coils of the magnet,

The microphone box B consists of a pair of rings 6 that are spaced apart by washers Z2, and which are clamped in place by bolts or studs 6 having their heads fastened to the front wall of the cap a, said bolts or studs having sleeves of insulation 5 that extend from the outer surface of said cap to the inner surface of the metal plate 5*, in the manner shown. A stationary electrode 71 engages the outer surface of one ring I), and

Patented Mar. 10, 1914.

a similar electrode 6 engages the outer surface of the other ring 6, whereby the opening through said rings is closed at front and back to form a chamber for the granular carbon b and for the movable or plunger-like electrode Z2 which divides the said carbon into two separate masses or bodies. These electrodes can be of carbon, or any other suitable material. The said stationary electrodes are backed by metal terminal plates 6 and b and these plates are insulated from the cap and the outer ,plate 6* respectively, by plates of insulation?) and 6 in the manner shown. Thus, the superintposed layers of metal, carbon and insulation are all clamped tightly in place and upon each other to form a box or hollow structure. The electrode 11 is connected by a stem I) with the diaphragm a, said electrode being secured to the said stem by nuts which engage the threaded portion of the stem, whereby the electrode can be adjusted properly on the stem. The space between the opposing surfaces of 'therings b is filled with soft fibrous material I), such as fluffy asbestos or other similar material, which engages the outer edges of the electrode Z3 and which prevents the granular carbon fromescaping at the circumference of the micro phone box.

Thus it will be seen that I provide an improved diilerential microphone repeater in which the stem of the flexible electrode extends through only one side of the box, and in which the latter is of simple and efiicient construction, and of such character that heavy currents can be carried without danger of overheating or other trouble. The air gap between the diaphragm a and the pole pieces can be accurately regulated by the adjustment of the screw threaded cap a, which is then locked in place by a threaded ring or lock nut a", it being understood that the first or approximate adjustment of these different parts is obtained by properly adjusting the electrode 6 on the stem 6 at the time thatthe same is secured thereon bythe said nuts or other suitable devices. The said microphone box can be easily taken apart for the purpose of repair or substitution. It can be filled with the granular carbon before the front and back plates or dislelike electrodes are secured in place. The insulating parts of the microphone box can be of any suitable character, such as mica onfiber or rubber vulcanite, or any other suitable insulating material that can stand considerable heat if it becomes necessary to employ heavy currents.

With the construction shown, it will be ob served that the-granular carbon at one side of the movable electrode is separated from the granular carbon at the other side thereof. This does not interfere with the free and proper vibration of the said electrode, and the results, I find, with this construction, entirely satisfactory. lit will be seen that similar packing of fibrous material 25 placed around the stem in the perforation of the back electrode, whereby the granular carbon is prevented from escaping at this point.

When the cap a is removed, it carries with it the entire microphone device, and also carries with it the diaphragm by which the microphoneis operated, thus facilitating adjustment of these parts for accurate operation thereof. Also, the adjustmentof the air gap between the diaphragm and the mag-- net is accomplished by adjusting both the diaphragm and the microphone. in other words, the microphone and diaphragm are moved toward and away from the magnet to regulate the air gap. 1

What I claim as my invention is l. in a microphone repeater, a miciophone box provided with a movable stem for the operation thereof, a magnet, a diaphragm. disposed in position to be directly acted upon and vibrated by said magnet, said diaphragm being connected with the said stem, a cup partially inclosing said magnet, and a re movable cap screwed upon the said cup, which cap carries with it when romo ed both the said diaphragm and said microphone box, said diaphragm being mounted on one side of said cap and the microphone box on the other side thereof.

9.. In a microphone repeater, a magnet, a

cup partially inclosing said magnet, a cap for said cup removably secured thereto, a diaphragm mounted adjacent the poles of said magnet and carried by said cap, a mi crophone transmitter mounted on the outside of said cap, and a connection between said. diaphragm and said transmitter i assing through said cap.

Signed by me at Chicago, Illinois, this 18th day of Feb. 1911.

JOHN J. CGMER.

Witnesses R. l lnanns,

E. H. CLnee.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner oi Eatents,

Washington. 1 E. 

